Different types of spectrophotometers for analyzing laboratory samples that make it possible, among others, to carry out a spectral analysis of a sample with respect to a reference are known in the state of the art. The spectrophotometry process consists in using a light beam (of different wavelengths according to the analysis that is to be carried out), directing it to the sample, and analyzing the light transmitted or reflected by that sample.
In the field of standard spectrophotometry, the existing solutions are made to measure the overall optical properties of a sample, which is usually a liquid sample placed in a cuvette and measured in transmission; therefore, the spectral measurements do not have spatial resolution, as stated, for example, in document US 2013/0130400. Nevertheless, many scientific and technical applications require optical characterization of a surface with high spatial resolution, and therefore, a standard spectrophotometry system is not suitable for the entire range of applications.
In the literature there are different technical solutions for the spatially-resolved spectral analysis of a surface, also known as micro-spectrophotometric techniques. The most commonly used solution consists in coupling a spectrometer to an optical microscope by means of an optical fiber. The collimated beam of a light source is focused by means of a lens on the sample and the light that comes from a small region of the sample is analyzed by means of an optical fiber placed on the image plane of the optical microscope. Nevertheless, although this solution obtains acceptable results, it is conditioned by the diameter of the optical fiber, and furthermore, several calibrations are needed, as well as the alignment of the optical fiber, said tasks requiring a significant amount of the user's time and that said users are, or at least have access to, personnel specialized in these types of measurements.
There are other types of technical solutions that do not require an optical fiber to carry out the spectrophotometric analysis, since they already incorporate a special pierced mirror and light is transmitted through said holes instead of using the optical fiber.
These two solutions produce good spatial resolution, but they have the significant disadvantage that the spatial mapping (also called surface scanning throughout the specification) of a sample must be performed sequentially by a mechanical scanning system which always tends to be very slow. Spatial resolution in these two systems is going to be limited and established by the diameter of the fiber or mirror hole and by the accuracy of the scanning system.
Another disadvantage of these two systems is that it is always necessary to take each one of the measurements with a reference sample in order to eliminate the spectral dependency of the photodetectors, the light source and all optical components.